This invention relates to the preparation of glycosylated insulins. More particularly, this invention relates to the preparation of glycosylated insulins and to novel intermediates to be used in preparing glycosylated insulins.
Various systems have been proposed for the delivery of insulin to a diabetic patient that will be more responsive to the needs of the patient.
The bioengineering approach is directed towards design of insulin infusion pumps. Hundreds of diabetics presently use external battery-operated pumps. The pump injects insulin continuously through a needle attached to a catheter inserted into a vein or into subcutaneous tissue. The flow can be adjusted manually when a change occurs in the amount of insulin needed. The units are usually worn on a belt or strapped to a leg.
Still in an experimental stage are pumps that deliver an amount of insulin precisely determined by a sensor that measures blood glucose levels. Though successful progress has been made in this area, these pumps are still too heavy to be portable. Another difficulty is that the system needs an apparatus for the continuous sampling of blood, an analyzer to determine the blood glucose level rapidly and continuously, a computer to analyze the results and to determine the appropriate insulin dose, and an infusion pump to deliver insulin intravenously in a manner approximating the delivery by the beta cells of the pancreas. Efforts are underway to reduce the size of the system and prolong its sensor's life. A "vest pocket" model, a system the size of a cigarette pack containing glucose sensor, power source, computer, insulin reservoir and pump, has been reported by Elliot in J. Am. Med. Assoc., 241, 223 (1979).
Another obstacle at present is the lack of an accurate implantable electrode to sensor the concentration of blood glucose. Again, a through-the-skin connection to the patient's blood stream for long periods presents risks of infection and clotting problems. Also, the occurring aggregation of insulin in the artificial delivery systems poses a considerable problem since the aggregated insulin will precipitate or crystallize out of solution, thereby reducing the bioavailability of the insulin in an insulin reservoir. In addition, the aggregated insulin can become lodged in the delivery needle and prevent the flow of insulin from the delivery system to the diabetic.